Somehow it feels like the linq to sql class should inform the listbox that it needs to refresh and there should be some magic setting, but for the time being:
XAML extract:
set the datasource in the window:
<Window x:Class="HomerV3_Queries.Window_Queries"
DataContext="{Binding RelativeSource={RelativeSource Self}}"
bind to it at the listbox. "Queries" is the table I'm binding to.:
ItemsSource="{Binding Path=Queries,UpdateSourceTrigger=PropertyChanged}"

C# code called after every database change – note the commented out stuff that does not work: